This invention relates to heat storage ponds such as solar collectors, and to methods of and means for creating such ponds.
U.S. Pat. No. 4,091,800 discloses construction of a solar collector on the order of several acres in size. Such construction involves lining a large number of shallow trenches about 1-2 feet deep with a water impermeable plastic sheet, adding water to a depth of about one foot to the trenches, and floating a transparent plastic sheet on the surface of the water. The remaining height of each of the trenches is filled with clear water or with a transparent solid such as a gelatinous mass. The lower level of water is heated by its absorption of solar radiation that penetrates the gelatinous mass which serves to prevent heat loss from the water to the ambient medium above the gelatinous mass. There is no disclosure in this patent, however, of the nature of the gel, of a procedure for producing it on the scale contemplated, or of the constituents that will produce a gel that will be transparent to and stable in the presence of solar radiation.
British Provisional patent specification No. 1/9401/77 filed May 9, 1977 discloses a solar collector in which an aqueous gel of cross-linked polyacrylamide floats on a layer of water. The gel is transparent to solar radiation allowing the lower layer of water to be heated to a temperature approaching the boiling point.
The in situ production of an aqueous gel to cover a large-scale solar pond is a formidable task when starting with the monomeric constituents of the gel. The basic problem appears to be the inhibiting effect of atmospheric oxygen on the polymerization process by which the gel structure is formed after the monomeric constituents have been poured out on top of the heat collecting layer of the pond. The adverse effects of the atmospheric oxygen on the polymerization process is conventionally prevented in small-scale laboratory production by carrying out the polymerization process under an inert atmosphere such as a blanket of argon, nitrogen, CO.sub.2, etc. which excludes atmospheric oxygen during the polymerization process. For obvious reasons, the above described laboratory expedient is impractical when constructing a large-scale solar pond under field conditions. It is therefore, an object of the present invention to provide a new and approved gel, as well as a new and approved method for preparing it under field conditions in the presence of atmospheric oxygen.